js-optchain

This package adds schema-based optional chaining to javascript. Simply wrap the object with the oc and define your default schema. This will create an object containing all fields specified in the schema with the existing values or default ones from the schema if the data is undefined. The optional chain is recursively generated so schemas can be multi-level. See Usage for examples.

Installation

NPM:

npm install js-optchain

Yarn:

yarn add js-optchain

Importing:

With import:

import oc from "js-optchain";

With require:

const oc = require("js-optchain").default;

Usage

/**
 * Wrap an object with optional properties which should have default values if undefined.
 *
 * To use partials, set the element in the schema to `{}`
 *
 * Partials are enabled by default. If partials are not enabled, the output will strictly match the schema shape.
 *
 * @param {*} optionalObj The object to wrap
 * @param {*} schema The schema with default values which should be returned
 * @param {*} allowPartials (Optional) True if elements in the wrapped object should be included even if they don't appear in the schema
 */
const ocObj = oc(obj, schema, allowPartials);

• The first argument is the object you want to explore that may or may not be undefined.
• The second argument is the schema of its optional chain with default values.
• There is an optional third argument that defaults to true and allows partial schemas (see handler/ocBody 6 below for an example)
• The returned result is an object that will match the schema and have default values if the found values are undefined. This can include nested objects, see examples below.

Examples

Below are a series of examples that match the following. To view an example, see the handler, oc() and console.log for each number to see what the expected inputs and outputs are.

• ocBody1: Passing an undefined object into the oc wrapper (object is undefined)
• ocBody2: Passing an empty object into the oc wrapper (object has none of the schema properties)
• ocBody3: Passing a partial object into the oc wrapper (object only has some of the schema properties)
• ocBody4: Passing a complete object into the oc wrapper (object has all the schema properties)
• ocBody5: Passing a nested object into the oc wrapper (schema contains multiple layers)
• ocEvent5: Passing a more complex object into the oc wrapper
• ocEvent6: Passing an object into the oc wrapper with partials
• ocEvent6NoPartials: Passing an object into the oc wrapper with partials disabled

Therefore, all of these inputs are valid:

// import oc from "js-optchain";
const oc = require("js-optchain").default;
 
const handler1 = {
  event: {},
};
 
const handler2 = {
  event: {
    body: {},
  },
};
 
const handler3 = {
  event: {
    body: {
      username: "jeff",
    },
  },
};
 
const handler4 = {
  event: {
    body: {
      username: "jeff",
      password: "password",
    },
  },
};
 
const handler5 = {
  event: {
    body: {
      user: {
        username: "jeff",
      },
    },
  },
};
 
const handler6 = {
  event: {
    body: {
      user: {
        username: "jeff",
        password: "password",
      },
    },
  },
};
 
const ocBody1 = oc(handler1.event.body, {
  username: "defaultUsername",
  password: "defaultPassword",
});
const ocBody2 = oc(handler2.event.body, {
  username: "defaultUsername",
  password: "defaultPassword",
});
const ocBody3 = oc(handler3.event.body, {
  username: "defaultUsername",
  password: "defaultPassword",
});
const ocBody4 = oc(handler4.event.body, {
  username: "defaultUsername",
  password: "defaultPassword",
});
const ocBody5 = oc(handler5.event.body, {
  user: {
    username: "defaultUsername",
    password: "defaultPassword",
  },
});
const ocEvent5 = oc(handler5.event, {
  body: {
    user: {
      username: "defaultUsername",
      password: "defaultPassword",
    },
    config: {
      isAdmin: true,
    },
  },
});
const ocEvent6 = oc(
  handler6.event,
  {
    body: {
      user: {},
    },
  },
  false
);
const ocEvent6NoPartials = oc(
  handler6.event,
  {
    body: {
      user: {},
    },
  },
  false
);
 
console.log(
  ocBody1.username === "defaultUsername" &&
    ocBody1.password === "defaultPassword"
);
console.log(
  ocBody2.username === "defaultUsername" &&
    ocBody2.password === "defaultPassword"
);
console.log(
  ocBody3.username === "jeff" && ocBody3.password === "defaultPassword"
);
console.log(ocBody4.username === "jeff" && ocBody4.password === "password");
console.log(
  ocBody5.user.username === "jeff" &&
    ocBody5.user.password === "defaultPassword"
);
console.log(
  ocEvent5.body.user.username === "jeff" &&
    ocEvent5.body.user.password === "defaultPassword" &&
    ocEvent5.body.config.isAdmin === true
);
console.log(
  ocEvent6.body.user.username === "jeff" &&
    ocEvent6.body.user.password === "password"
);
console.log(ocEvent6NoPartials.body.user === {});